The present invention refers to devices adapted to transfer impacts to elongate members, in the first hand suited for the driving of piles, the device using an impact cap including a piston operating in a cylinder, a portion of said piston extending outside the cylinder for acting upon the member, for instance the head of a pile. The cylinder encloses a volume of pressurized gas.
This pressure which in use may vary between 20 bar and 250 bar, must for each stroke of the hammer be adjusted in response to the resistance offered by the ground, when a pile is driven thereinto.